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JavaScript Loop Performance Tests

This page may take a little while to become responsive as it's creating an array of 10,000,000 (10 million) items. It may also lock up completely on slow machines or older browsers. You are warned!

Standard post-increment for loop.

for(var i = 0; i < arr.length; i++) 
	arr[i];

Pre-increment loop counter.

for(var i = 0; i < arr.length; ++i) 
	arr[i];

Cached length value.

for(var i = 0, len = arr.length; i < len; i++) 
	arr[i];

Reverse loop.

for(var i = arr.length; i >= 0; i--) 
	arr[i];

jQuery each function.

$.each(arr, function(item) {
	item;
});

Underscore each function.

_.each(arr, function(item) {
	item;
});

Native forEach function, if the browser supports it.

arr.forEach(function(item) {
	item;
});